Current Automatic Dependent Surveillance (ADS) technology, such as Global Positioning System (GPS), Wide Area Augmentation System (WAAS) EGNOS, MTSAT or GLONASS, provides positioning information utilizing satellite communication. For example, the GPS, developed and deployed by the U.S. Department of Defense, consists of twenty-four satellites orbiting the earth twice a day at an altitude of 12,000 miles, as well as five ground stations to monitor and manage the satellite constellation. Using atomic clocks and location data, GPS satellites transmit continuous time and position information twenty-four hours a day to a GPS receiver, which listens to three or more satellites at once to determine the user's position on earth. By measuring the time interval between the transmission and the reception of a satellite signal, the GPS receiver calculates the distance between the user and each satellite, and then uses the distance measurements of at least three satellites to arrive at a position.
Such systems, however, utilize one-way ranging in which an accurate, synchronized clock is required at each station. Any synchronization error or error regarding the location of one of the satellites results in an error in the determined position of the target vehicle. An aircraft, or other target vehicle, must still have accurate position and velocity information and requires dedicated, precise equipment throughout the system to provide very accurate position and velocity information with a high degree of integrity and reliability.
In addition, a German system provides a novel non-cooperative near-range radar network for traffic guidance and control on airport surfaces, as stated in IEEE Trans. On Control System Technology, Vol. I, No. 3, September 1993. This ground-based tracking system uses non-cooperative radar for two-way transmission and employs triangulation ranging. Ground-based Loran-C systems require a hyperbolic electronic grid and are accordingly limited to local tracking. Other systems such as Radio Determination Satellite System (RDSS) using geostar and fire control, navigation and tracking systems with either non-cooperative or cooperative architectures are also limited ranging implementations.